DE112019006135T5 - Reducing agent injection device, exhaust gas processing device, and exhaust gas processing method - Google Patents

Abstract

A reducing agent injection apparatus 100 including: a honeycomb structure 1 including: a columnar honeycomb structure portion 11 having a partition 15 defining a plurality of cells 14 each extending from a fluid inflow end surface 13a to a fluid outflow end surface 13b; and at least one pair of electrode portions 12 configured to heat the honeycomb structure portion 11 by passing a current, the pair of electrode portions 12 being arranged on a side surface of the honeycomb structure portion 11, the honeycomb structure 1 configured to contain the urea decomposed in an aqueous urea solution in the honeycomb structure portion 11 heated by passing the current to generate ammonia; an outer cylinder 2 having an inlet-side end portion and an outlet-side end portion, the inlet-side end portion including a carrier gas introduction port 22 configured to introduce a carrier gas, the outlet-side end portion including an injection port 21 configured to inject ammonia, the outer cylinder 2 the Honeycomb structure 1 accommodates and a first flow path through which a fluid can flow through the plurality of cells 14, and a second flow path through which the fluid can flow from the inlet-side end portion to the outlet-side end portion without going through the plurality of cells 14 in the outer cylinder 2 are provided; a urea spray device 3 configured to spray the urea aqueous solution into the first flow path or the second flow path on an inflow side of the fluid, the urea spray device 3 being disposed at one end of the outer cylinder 2; and a spray direction switch configured to switch a spray direction of the urea aqueous solution into the first flow path or the second flow path depending on the temperatures of an exhaust gas.

Description

FIELD OF THE INVENTION

The present invention relates to a reducing agent injection device, an exhaust gas processing device, and an exhaust gas processing method.

BACKGROUND OF THE INVENTION

An exhaust gas processing apparatus using a NOx selective catalytic reduction (SCR) catalyst is known for purifying nitrogen oxides (NOx) in exhaust gases emitted from various engines (Patent Literature 1).

The exhaust gas processing apparatus described in Patent Literature 1 includes a catalyst (SCR catalyst) attached to an exhaust pipe of an engine and means for injecting urea water into the exhaust pipe between the engine and the catalyst, and also includes a plurality of urea water injection means for mixing Urea water with an exhaust gas, for reacting with specific components in the exhaust gas by the catalyst and for mixing the urea water with the exhaust gas.

In the exhaust gas processing apparatus described in Patent Literature 1, however, a temperature of the exhaust gas needs to be 200 ° C. or higher in order to decompose the urea in the urea water into ammonia by the heat of the exhaust gas. Therefore, when the temperature of the exhaust gas is lower, there is a problem that it is difficult for the decomposition reaction of urea to take place and an amount of ammonia required for the NOx treatment is insufficient.

Therefore, there has been proposed an exhaust gas processing device using a reducing agent injection device, the reducing agent injection device including: a honeycomb structure (a honeycomb heater) having a cylindrical honeycomb structure portion and a pair of electrode portions disposed on a side surface of the honeycomb structure portion; and a urea spray device configured to spray a urea aqueous solution onto the honeycomb structure portion (Patent Literature 2). The reducing agent injection device used in the exhaust gas processing device can spray the urea aqueous solution onto the honeycomb structure portion that has been electrically heated by applying a voltage to the electrode portions and decompose the urea in the urea aqueous solution in the honeycomb structure to efficiently generate ammonia.

However, by spraying the urea aqueous solution on the electrically heated honeycomb structure portion, a temperature of a region where the urea aqueous solution is sprayed decreases, thereby generating temperature irregularity in the honeycomb structure portion. As a result, urea deposits (crystals caused by urea) tend to be generated in a lower temperature region of the honeycomb structure portion. The generation of the urea scale blocks a flow path in the honeycomb structure portion, preventing the urea from decomposing into ammonia.

Therefore, exhaust gas processing devices using a reducing agent injection device provided with a carrier gas introduction port between the urea injection nozzle and the honeycomb structure have been proposed (Patent Literature 3 and 4). According to the reducing agent injection device used in each exhaust gas processing device, a carrier gas introduced from the carrier gas introduction port can promote the flow of the gas in the honeycomb structure portion. Therefore, even if the urea aqueous solution is sprayed on the honeycomb structure portion, a temperature difference in the honeycomb structure portion can be reduced, thereby suppressing the formation of urea scale.

LIST OF REPUTATIONS

Patent literature

• [Patent Literature 1] Japanese Patent Application Publication No. 2007-327377 A
• [Patent Literature 2] WO 2014/148506
• [Patent Literature 3] Japanese Patent Application Publication No. 2017-180298 A
• [Patent Literature 4] Japanese Patent Application Publication No. 2017-180299 A

SUMMARY OF THE INVENTION

The problem to be solved by the invention

An amount of the NOx in an exhaust gas is changed depending on the driving patterns of the automobiles. As the amount of NOx in the exhaust gas is higher, the amount of a reducing agent (ammonia) required to purify the NOx increases, so that the amount of the urea aqueous solution sprayed needs to be increased. The increased amount of the urea aqueous solution sprayed lowers the temperature of the honeycomb structure, so that an electric power for conducting a current needs to be increased, resulting in increased power consumption.

Furthermore, the amount of the reducing agent required to purify the NOx generally depends on the temperatures of the exhaust gas containing NOx. When the temperature of the exhaust gas is lower, the amount of reducing agent required is decreased, while when the temperature of the exhaust gas is higher, the amount of reducing agent required is increased. Further, when the temperature of the exhaust gas is higher (e.g., 200 ° C or higher), the urea is decomposed by the heat of the exhaust gas to generate ammonia even if the urea aqueous solution is sprayed directly into the exhaust gas, so that NOx can be cleaned. Therefore, ammonia can be sprayed from the reducing agent injection device when the temperature of the exhaust gas is lower, while when the temperature of the exhaust gas is higher, the urea aqueous solution can be sprayed from the reducing agent injection device.

However, the conventional reducing agent injection device described in each of Patent Literature 2 to 4 is not intended to spray the urea aqueous solution as it is. Therefore, when the amount of the urea aqueous solution sprayed is increased, the honeycomb structure portion obstructs the flow of the urea aqueous solution. This leads to problems that the urea aqueous solution cannot be efficiently injected from the reducing agent injection device and the urea scale is easily generated.

The present invention has been made to solve the above problems. It is an object of the present invention to provide a reducing agent injection device which has reduced power consumption and can select ammonia or an aqueous urea solution depending on the temperatures of the exhaust gas in order to efficiently inject the ammonia or the aqueous urea solution.

It is also another object of the present invention to provide an exhaust gas processing device and an exhaust gas processing method that can efficiently inject ammonia or an aqueous urea solution from the reducing agent injection device to purify NOx, depending on the temperatures of the exhaust gas.

Means of solving the problem

As a result of intensive studies for a structure of a reducing agent injection device including a honeycomb structure in which at least a pair of electrode portions are arranged on a side surface of a honeycomb structure portion, the inventors of the present invention have found that the above problems by forming a first flow path , through which a fluid can flow into the cells of the honeycomb structure portion, and a second flow path through which the fluid can flow without flowing through the cells of the honeycomb structure portion, in an outer cylinder for accommodating the honeycomb structure and the provision of a spray direction switch, the aqueous Urea solution may be sprayed into the first flow path or the second flow path depending on the temperatures of the exhaust gas, and they have completed the present invention.

• eine Wabenstruktur, die umfasst:
  • einen säulenförmigen Wabenstrukturabschnitt mit einer Trennwand, die mehrere Zellen definiert, die sich jeweils von einer Fluideinströmstirnfläche zu einer Fluidausströmstirnfläche erstrecken; und
  • wenigstens ein Paar von Elektrodenabschnitten, die konfiguriert sind, den Wabenstrukturabschnitt durch das Leiten eines Stroms zu erwärmen, wobei das Paar von Elektrodenabschnitten an einer Seitenfläche des Wabenstrukturabschnitts angeordnet ist, wobei die Wabenstruktur so konfiguriert ist, dass sie Harnstoff in einer wässrigen Harnstofflösung in dem durch das Leiten des Stroms erwärmten Wabenstrukturabschnitt zersetzen kann, um Ammoniak zu erzeugen;
  • einen Außenzylinder mit einem einlassseitigen Endabschnitt und einem auslassseitigen Endabschnitt, wobei der einlassseitige Endabschnitt eine Trägergaseinleitungsöffnung umfasst, die konfiguriert ist, ein Trägergas einzuleiten, wobei der auslassseitige Endabschnitt eine Einspritzöffnung umfasst, die konfiguriert ist, Ammoniak einzuspritzen, wobei der Außenzylinder die Wabenstruktur unterbringt und ein erster Strömungsweg, durch den ein Fluid durch die mehreren Zellen strömen kann, und ein zweiter Strömungsweg, durch den das Fluid von dem einlassseitigen Endabschnitt zu dem auslassseitigen Endabschnitt strömen kann, ohne durch die mehreren Zellen zu gehen, in dem Außenzylinder vorgesehen sind;
  • eine Harnstoffsprühvorrichtung, die konfiguriert ist, die wässrige Harnstofflösung in den ersten Strömungsweg oder den zweiten Strömungsweg auf einer Einströmseite des Fluids zu sprühen, wobei die Harnstoffsprühvorrichtung an einem Ende des Außenzylinders angeordnet ist; und
  • einen Sprührichtungsschalter, der so konfiguriert ist, dass er eine Sprührichtung der wässrigen Harnstofflösung abhängig von den Temperaturen eines Abgases in den ersten Strömungsweg oder in den zweiten Strömungsweg umschalten kann.

Accordingly, the present invention relates to a reductant injection device comprising:

• a honeycomb structure that includes:
  • a columnar honeycomb structure portion having a partition wall defining a plurality of cells each extending from a fluid inflow end surface to a fluid outflow end surface; and
  • at least one pair of electrode portions configured to heat the honeycomb structure portion by passing a current, the pair of electrode portions being arranged on a side surface of the honeycomb structure portion, the honeycomb structure configured to contain urea in an aqueous urea solution conducting the current can decompose heated honeycomb structure portion to produce ammonia;
  • an outer cylinder having an inlet-side end portion and an outlet-side end portion, the inlet-side end portion including a carrier gas introduction port configured to introduce a carrier gas, the outlet-side end portion including an injection port configured to inject ammonia, the outer cylinder accommodating the honeycomb structure and a first flow path through which a fluid can flow through the plurality of cells and a second flow path through which the fluid can flow from the inlet-side end portion to the outlet-side end portion without passing through the plurality of cells are provided in the outer cylinder;
  • a urea spray device configured to spray the urea aqueous solution into the first flow path or the second flow path on an inflow side of the fluid, the urea spray device being disposed at one end of the outer cylinder; and
  • a spray direction switch configured to switch a spray direction of the urea aqueous solution into the first flow path or the second flow path depending on the temperatures of an exhaust gas.

• eine Abgasleitung, durch die ein Abgas strömt;
• die Reduktionsmittel-Einspritzvorrichtung, die konfiguriert ist, Ammoniak oder eine wässrige Harnstofflösung in die Abgasleitung einzuspritzen; und
• einen SCR-Katalysator, der an dem Abgaszylinder auf einer stromabwärts gelegenen Seite einer Position angeordnet ist, an der das Ammoniak oder die wässrige Harnstofflösung eingespritzt wird.

The present invention further relates to an exhaust gas processing device comprising:

• an exhaust pipe through which an exhaust gas flows;
• the reducing agent injection device configured to inject ammonia or an aqueous urea solution into the exhaust pipe; and
• an SCR catalyst disposed on the exhaust cylinder on a downstream side of a position where the ammonia or the urea aqueous solution is injected.

• Einspritzen einer wässrigen Harnstofflösung in das Abgas von der Reduktionsmittel-Einspritzvorrichtung und Reduzieren des mit der wässrigen Harnstofflösung vermischten Abgases durch einen SCR-Katalysator, wenn eine Temperatur des Abgases 200 °C oder höher ist; und
• Einspritzen von erzeugtem Ammoniak in das Abgas durch die Reduktionsmittel-Einspritzvorrichtung und Reduzieren des mit dem Ammoniak vermischten Abgases durch den SCR-Katalysator, wenn eine Temperatur des Abgases tiefer als 200 °C ist.

The present invention further relates to a method for processing an exhaust gas, the method comprising:

• Injecting an aqueous urea solution into the exhaust gas from the reducing agent injection device and reducing the exhaust gas mixed with the aqueous urea solution by an SCR catalyst when a temperature of the exhaust gas is 200 ° C or higher; and
• Injecting generated ammonia into the exhaust gas by the reducing agent injection device and reducing the exhaust gas mixed with the ammonia by the SCR catalyst when a temperature of the exhaust gas is lower than 200 ° C.

Effects of the invention

According to the present invention, it is possible to provide a reducing agent injection device that has reduced power consumption and can select ammonia or an aqueous urea solution depending on the temperatures of an exhaust gas to efficiently inject the ammonia or the aqueous urea solution.

In addition, according to the present invention, it is possible to provide an exhaust gas processing device and an exhaust gas processing method that can efficiently inject ammonia or an aqueous urea solution from the reducing agent injection device to purify NOx, depending on the temperatures of an exhaust gas.

Figure list

• 1 Fig. 13 is a schematic cross-sectional view showing a reducing agent injection device according to Embodiment 1 of the present invention;
• 2 is one along line AA 'in 1 considered schematic cross-sectional view;
• 3 Fig. 13 is a schematic cross-sectional view showing a reducing agent injection device according to Embodiment 2 of the present invention;
• 4th is one along the line BB 'in 3 considered schematic cross-sectional view;
• 5 is one along the line CC 'in 3 considered schematic cross-sectional view;
• 6th Fig. 3 is a schematic cross-sectional view showing an exhaust gas processing device according to Embodiment 3 of the present invention; and
• 7th Fig. 13 is a schematic cross-sectional view showing another exhaust gas processing device according to Embodiment 3 of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

In the following, preferred embodiments of a reducing agent injection device, an exhaust gas processing device and a method for processing an exhaust gas according to the present invention will be specifically described with reference to the drawings. It should be understood that the present invention is not limited to the following embodiments, those with changes, improvements and the like suitably added to the following embodiments based on the knowledge of those skilled in the art without departing from the gist of the present invention are shown in FIG fall within the scope of the present invention. Some components can e.g. B. can be deleted from all components set out in the embodiments, or components of different embodiments can optionally be combined.

<Embodiment 1>

(1) Reducing agent injection device

1 FIG. 13 is a schematic cross-sectional view showing a reducing agent injection device according to Embodiment 1 of the present invention (a schematic cross-sectional view parallel to an extending direction of FIG Cells of a honeycomb structure section). Furthermore is 2 one along line AA 'in 1 considered schematic cross-sectional view (a schematic cross-sectional view perpendicular to the extension direction of the cells of the honeycomb structure portion).

As in the 1 and 2 shown includes a reductant injector 100 according to the present embodiment: a honeycomb structure 1 ; an outer cylinder 2 showing the honeycomb structure 1 houses; and a urea sprayer 3 at one end of the outer cylinder 2 is arranged.

The honeycomb structure 1 includes: a columnar honeycomb structure portion 11 with a partition 15th who have favourited multiple cells 14th defined that extends from a fluid inflow face 13a to a fluid outflow face 13b extend; and at least a pair of electrode sections 12th configured, the honeycomb structure portion 11 by passing a current to heat, the electrode sections 12th on a side surface of the honeycomb structure section 11 are arranged. The honeycomb structure section 11 has a hollow structure configured to be at a center in a cross section perpendicular to the extending direction of the cells 14th a room area is located. In the hollow honeycomb structure section 11 with such a structure, the cells form 14th a first flow path and the spatial area forms a second flow path 16 .

The "fluid inflow face 13a “, As used here, means an end face with a fluid inflow opening, while the“ fluid outflow end face 13b “Means an end face with a fluid outflow opening. Further, the “pair of electrode sections 12th “From the standpoint of uniformly heating the honeycomb structure portion 11 preferably arranged so that an electrode section 12th in a cross section orthogonal to the direction of extension of the cells 14th of the honeycomb structure section 11 across the center of the honeycomb structure section 11 on an opposite side of the other electrode section 12th is arranged.

The electrode section 12th is preferably along the extension direction of the cells 14th formed in a band shape. A pair of electrode sections 12th is preferred, but with pairs of electrode sections 12th in terms of increasing a heat generation efficiency of the honeycomb structure portion 11 possible are.

The outer cylinder 2 has an inlet-side end section and an outlet-side end section and brings the honeycomb structure 1 in it under. The inlet-side end portion, which is one end, is provided with a carrier gas introduction port 22nd which is configured to introduce a carrier gas. The inlet-side end section is also connected to the urea spray device 3 Mistake. The outlet end, which is the other end, is with an injection port 21 configured to inject ammonia.

Inside the outer cylinder 2 are a first flow path through which a fluid enters the cells 14th of the honeycomb structure section 11 can flow, and a second flow path through which the fluid can flow from the inlet-side end portion to the outlet-side end portion without passing through the cells 14th to go, provided. That is, inside the outer cylinder 2 are the first flow path (the cells 14th ) and the second flow path 16 in the longitudinal direction of the outer cylinder 2 arranged in parallel. Because the second flow path 16 is configured so that the fluid passes through a different section than the cells 14th of the honeycomb structure section 11 can flow, the fluid flows either through the first flow path (the cells 14th ) or the second flow path 16 .

The carrier gas inlet opening 22nd is preferably on the side of the fluid inflow end face 13a of the honeycomb structure section 11 , that is, between the honeycomb structure 1 and the urea spray device 3 intended. Non-limiting examples of the carrier gas that can be used include exhaust gases, intake gases, and air from other air supply devices (compressors and the like mounted on large vehicles and the like).

The one in the outer cylinder 2 housed honeycomb structure 1 is via an insulation holding section 23 in the outer cylinder 2 attached (held). This can enable insulation between the honeycomb structure 1 and the outer cylinder 2 is ensured. There may be a section (room) in which the insulation holding section 23 not between the honeycomb structure 1 and the outer cylinder 2 is arranged, but the entire outer periphery of the honeycomb structure 1 with the insulation holding section 23 can be covered. A material of the insulation holding portion 23 is not particularly limited as long as it has excellent insulating properties. where z. B. alumina, glass or the like can be used.

The urea spray device 3 is at one end (inlet side end portion) of the outer cylinder 2 arranged and sprays an aqueous urea solution on the side of the fluid inflow end face 13a of the honeycomb structure section 11 . Furthermore, the urea spray device 3 a spray direction switch configured to switch a spray direction of the urea aqueous solution depending on the temperatures of the exhaust gas to the first flow path (cells 14th ) or the second flow path 16 can switch.

The reductant injector 100 According to the present embodiment having the above structure, the urea aqueous solution sprays from the urea sprayer 3 depending on the temperatures of the exhaust gas in the first flow path (the cells 14th ) or the second flow path 16 . The urea in the aqueous urea solution that enters the first flow path (the cells 14th ) is sprayed through by directing the current in the first flow path (the cells 14th ) heated honeycomb structure section 11 decomposes to produce ammonia (a reducing agent), the ammonia via the injection port 21 is injected to the outside. On the other hand, the one in the second flow path 16 sprayed aqueous urea solution through the injection port 21 injected directly to the outside. In this case, the introduction of the carrier gas into the outer cylinder 2 the flow of gas in the first flow path (the cells 14th ) and in the second flow path 16 produce. This prevents the aqueous urea solution from entering the first flow path (the cells 14th ) and in the second flow path 16 stagnates, whereby urea deposits are suppressed.

The following describes the reducing agent injection device 100 according to the present embodiment will be described in detail for each component.

(1-1) Honeycomb structure 1

The honeycomb structure 1 contains the honeycomb structure section 11 and the electrode sections 12th .

The partition 15th who have favourited the honeycomb structure section 11 may preferably be made of ceramics, although it is not particularly limited thereto. In particular, the partition contains 15th preferably a silicon-silicon carbide composite material or silicon carbide as a main component, and more preferably a silicon-silicon carbide composite material as a main component. The use of such a material can enable the specific electrical resistance of the honeycomb structure section 11 is simply set to any value by changing a ratio of silicon carbide and silicon.

The “silicon-silicon carbide composite material” as the main component as used herein means a material containing silicon carbide particles as an aggregate and metallic silicon as a binding material for binding the silicon carbide particles. In the silicon-silicon carbide composite material, it is preferable that a plurality of silicon carbide particles are bonded by metallic silicon. Further, the “silicon carbide” as the main component means a material formed by sintering silicon carbide particles. Furthermore, as used herein, the “main component” means a component contained in an amount of 90 mass% or more.

The honeycomb structure section 11 preferably has an electrical resistivity of 0.01 to 500 Ωcm, and more preferably 0.1 to 200 Ωc, although it is not particularly limited. Control of the electrical resistivity at such a level can make the honeycomb structure portion 11 by applying a voltage to at least a pair of electrode sections 12th heat effectively. To in particular the honeycomb structure section 11 to be heated to 160 to 600 ° C using a power source having a voltage of 12 to 200 V, the electrical resistivity is preferably in the above range.

The specific electrical resistance of the honeycomb structure section 11 is a value at 25 ° C. The specific electrical resistance of the honeycomb structure section 11 is a value measured by a four-terminal method.

The honeycomb structure section 11 preferably has an area per unit volume of 5 cm ² / cm ³ or greater and more preferably from 8 to 45 cm ² / cm ³ and particularly preferably from 20 to 40 cm ² / cm ³ . The area of 5 cm ² / cm ³ or more can enable a sufficient contact area with the urea aqueous solution to be secured, thereby appropriately controlling a treatment rate of the urea aqueous solution, that is, an amount of ammonia generated (a generation rate).

The area of the honeycomb structure section 11 is an area of the surfaces of the partition 15th of the honeycomb structure section 11 .

The partition 15th of the honeycomb structure section 11 preferably has a thickness of 0.06 to 1.5 mm, and more preferably 0.10 to 0.80 mm. The thickness of the partition 15th of 1.5 mm or less can reduce a pressure loss, thereby appropriately controlling the treatment rate of the urea aqueous solution, that is, the amount of ammonia generated (generation rate). The thickness of the partition 15th of 0.06 mm or larger can prevent the honeycomb structure portion 11 destroyed by a thermal shock caused by heating by electrical conduction.

If the shape of each cell 14th (the shape of the cross-section orthogonal to the direction of extension of the cell 14th ) is circular, as in 2 means the thickness of the partition wall 15th a thickness of a portion in which “a distance between cells 14th the shortest is (a section in which the thickness of the partition 15th is less) ".

The cells 14th preferably have a density of 7 to 140 cells / cm ² and more preferably 15 to 120 cells / cm ² . The density of the cells 14th of 7 cells / cm ² or more can enable a sufficient contact area with the urea aqueous solution to be secured, thereby appropriately controlling the treatment rate of the urea aqueous solution, that is, the amount of ammonia generated (generation rate). The density of the cells 14th of 140 cells / cm ² or less can reduce the pressure loss, thereby appropriately controlling the treatment rate of the urea aqueous solution, that is, the amount of ammonia generated (generation rate).

The honeycomb structure section 11 can have some cells 14th having sealing portions at the end portion on the side of the fluid inflow end face 13a are provided. The material of the sealing portions is preferably the same as that of the partition wall 15th but other materials can be used.

A shape (outer shape) of the fluid inflow face 13a is not particularly limited, taking various forms such as B. like a square, a rectangle or other polygons and an ellipse, in addition to the one in 2 may have circular shape shown. Furthermore, the shape (outer shape) of the fluid inflow end face 13a the same as that of the fluid discharge face 13b and preferably like the shape (outer shape) of the cross section orthogonal to the direction of extension of the cells 14th .

The size of the honeycomb structure section 11 is such that the surfaces of the fluid inflow end face 13a and the fluid outflow face 13b that is the second flow path 16 contain, (the area of the cross-section orthogonal to the direction of extension of the cells 14th ) each from 50 to 10,000 mm ² and more preferably from 100 to 8,000 mm ² . Furthermore, the area of the second flow path is 16 in cross section orthogonal to the direction of extension of the cells 14th preferably from 20 to 2000 mm ² .

The shape of each cell 14th in cross section orthogonal to the direction of extension of the cell 14th is in addition to the in 2 The circular shape shown is preferably an ellipse, a square, a hexagon, an octagon or a combination thereof. Such a shape can reduce the pressure loss when the exhaust gas passes through the honeycomb structure portion 11 is passed, whereby the urea in the aqueous urea solution is efficiently decomposed.

The shape of the second flow path 16 , the one in the middle of the honeycomb structure section 11 is provided, z. B. in addition to the circle as in 2 is shown various forms, such as. B. a square, a rectangle or other polygons and ellipses, in cross section perpendicular to the direction of extension of the cells 14th although he is not particularly restricted to it.

The shape (outer shape) of the honeycomb structure portion 11 and the shape of the second flow path 16 may be the same or different, but they are preferably the same in terms of resistance to external influences, thermal stress and the like.

Each electrode section 12th is in a ribbon shape along the extending direction of the cells 14th formed, but may be formed in a wider width extending in the circumferential direction of the honeycomb structure portion 11 extends. Furthermore, the cross section is orthogonal to the direction of extension of the cells 14th an electrode section 12th on the opposite side of the other electrode section 12th arranged with the center of the honeycomb structure section 11 is arranged in between. Such a configuration can allow any biasing of the in the honeycomb structure portion 11 current flowing is suppressed when the voltage between the pair of electrode portions 12th is applied so that the bias of heat generation in the honeycomb structure portion 11 can be suppressed.

Furthermore, the application of the voltage to the electrode portions heats 12th preferably the honeycomb structure section 11 so that the temperature of the fluid inflow face 13a 900 ° C or less. The temperature of the honeycomb structure section 11 can by the direct provision of temperature measuring means on the honeycomb structure section 11 be controlled directly. Alternatively, it is also possible to measure the temperature of the honeycomb structure section 11 to estimate and control from a temperature of the carrier gas, a flow rate of the carrier gas and the amount of the sprayed aqueous urea solution. Furthermore, if the operating conditions of the engine are mapped, the mapping can be replaced by the measurement of the temperature of the carrier gas and the flow rate of the carrier gas.

The material of the electrode sections 12th is preferably the same as the main component the partition 15th of the honeycomb structure section 11 although it is not particularly limited to it.

The electrode sections 12th preferably have an electrical resistivity of from 0.0001 to 100 Ωcm, and more preferably from 0.001 to 50 Ωcm. The specific electrical resistance of the electrode sections 12th in such a range can allow the pair of electrode portions 12th effectively plays the role of electrodes in an exhaust pipe through which an exhaust gas at an elevated temperature flows. The specific electrical resistance of the electrode sections 12th is preferably smaller than that of the honeycomb structure portion 11 .

The specific electrical resistance of the electrode sections 12th is a value at 400 ° C. The specific electrical resistance of the electrode sections 12th is a value measured by the four-terminal method.

The pair of electrode sections 12th may with electrode terminal protrusion portions 17th for connecting electrical wiring 19th be provided from the outside. The material of the electrode terminal protruding portions 17th can be a conductive ceramic or a metal. Further, the material is the electrode terminal protruding portions 17th preferably the same as that of the electrode sections 12th . Further, it is preferable that each electrode terminal protruding portion 17th and a connector 18th of the outer cylinder 2 through the electrical wiring 19th are connected.

The honeycomb structure section 11 can be provided with a urea hydrolysis catalyst. Using the urea hydrolysis catalyst, ammonia can be efficiently produced from urea. Examples of the urea hydrolysis catalyst include titanium oxide and the like.

(1-2) outer cylinder 2

The outer cylinder 2 is preferably made of stainless steel or the like, although it is not particularly limited thereto.

Around the outer cylinder 2 to the honeycomb structure 1 adjust, instructs the outer cylinder 2 in cross section orthogonal to the direction of extension of the cells 14th preferably the same type of shape as that of the honeycomb structure portion 11 on. As "the same type of shape" is used here, it means that if the shape of the outer cylinder 2 is square, the shape of the honeycomb structure portion 11 also is square while if the shape of the outer cylinder 2 is rectangular, the shape of the honeycomb structure portion 11 is also rectangular. If z. B. the shapes of the outer cylinder 2 and the honeycomb structure portion 11 are of the same type and their shapes are rectangular, it is not necessary that both have the same length to width ratio.

(1-3) Urea spray device 3

The urea spray device 3 has a spray direction switch configured to switch the spray direction of the urea aqueous solution to the first flow path (the cells 14th ) or the second flow path 16 can switch.

Non-limiting examples of the spray direction switch that can be used include a nozzle that can change the spray direction of the urea aqueous solution depending on the feed pressures of the urea aqueous solution. Specific examples of the spray direction switch that can be used include a nozzle that feeds the urea aqueous solution into the second flow path 16 can spray when the feed pressure of the aqueous urea solution is lower, and the aqueous urea solution into the first flow path (the cells 14th ) can spray when the feed pressure of the aqueous urea solution is higher. In addition, when the spray direction switch is used, a small amount of a portion of the urea aqueous solution discharged from the urea spray device 3 is injected, flow into the first flow path when the urea aqueous solution through the spray direction switch into the second flow path 16 is sprayed.

The type of urea spray device 3 is not particularly limited as long as it can spray the urea aqueous solution. It is preferably a solenoid type, an ultrasonic type, a piezoelectric actuator type, or an atomizer type. Using this, the urea aqueous solution can be easily sprayed in the form of mists. Further, among them, the use of the solenoid type, the ultrasonic type, or the piezoelectric actuator type can enable the urea aqueous solution to be sprayed in the form of mists without using air. This can eliminate the need to heat the air used to spray the urea aqueous solution, thereby reducing an amount of energy to be heated. Further, because the injection volume is reduced by not using the air used for spraying, the speed at which the urea aqueous solution in the form of mist through the honeycomb structure portion can be reduced 11 passes through, which leads to a prolonged reaction time required for the decomposition. The size (diameter) of each droplet produced by the urea spray device 3 sprayed watery Urea solution is preferably 0.3 mm or smaller. If the size of the droplet is larger than 0.3 mm, it may be difficult to evaporate when it is in the honeycomb structure section 11 is heated.

Here is the urea spray device 3 solenoid type means a device that sprays the urea aqueous solution by vibrating the solenoid or by reciprocating a piston by an electric field using the solenoid. Further is the urea spray device 3 ultrasonic type means a device that sprays the urea aqueous solution in the form of mists by ultrasonic vibration. Furthermore, there is the urea spray device 3 of the piezoelectric actuator type, a device that sprays the urea aqueous solution in the form of mist by vibration of a piezoelectric element. Furthermore is the urea spray device 3 of the atomizer type z. B. a device that sprays the solution by sucking the solution with a tube and blowing the sucked solution up to a tip of the tube in the form of mists using air. The urea spray device 3 of the atomizer type may be a device in which a plurality of small openings are formed at the tip of the nozzle and the solution is sprayed from the openings in the form of mists.

At the urea spray device 3 The spraying direction (the direction in which the droplets are ejected) of the urea aqueous solution is preferably toward the fluid inflow end face side 13a of the honeycomb structure section 11 directed to the spraying of the urea aqueous solution on the side of the fluid inflow end face 13a of the honeycomb structure section 11 to promote.

Next, the method for manufacturing the reducing agent injection device will be discussed 100 according to the present embodiment will be described in detail.

(2) Method of manufacturing the reducing agent injection device 100

(2-1) Manufacture of the honeycomb structure 1

• Das Verfahren zum Herstellen der Wabenstruktur 1 enthält: einen Herstellungsschritt eines Wabenformlings; einen Herstellungsschritt eines getrockneten Wabenkörpers; einen Herstellungsschritt eines Wabenkörpers mit ungebrannten Elektroden und einen Herstellungsschritt einer Wabenstruktur.

If the honeycomb structure 1 Made of ceramic is the method of making the honeycomb structure 1 preferably as follows:

• The method of making the honeycomb structure 1 includes: a honeycomb molding manufacturing step; a drying honeycomb manufacturing step; a manufacturing step of a honeycomb body with unfired electrodes and a manufacturing step of a honeycomb structure.

(Manufacturing step of a honeycomb molding)

The honeycomb molding step preferably includes extruding a molding raw material to produce a honeycomb molding. The molding raw material preferably contains a ceramic raw material and an organic binder. In addition to the ceramic raw material and the organic binder, the molding raw material may further contain a surfactant, a sintering aid, a pore former, water and the like. The molding raw material can be obtained by mixing these raw materials.

The ceramic raw material in the molding raw material is a "ceramic" or "a raw material that forms a ceramic by firing". In any case, the ceramic raw material forms a ceramic after firing. The ceramic raw material in the molding raw material preferably contains metallic silicon and silicon carbide particles (silicon carbide powder) as the main components or silicon carbide particles (silicon carbide powder) as a main component. This can be the resulting honeycomb structure 1 provided with conductivity. The metallic silicon is also preferably composed of metallic silicon particles (metallic silicon powder). The wording “contains metallic silicon and silicon carbide particles as the main components” means that the total mass of metallic silicon and silicon carbide particles is 90 mass% or more of the whole (ceramic raw material). Examples of components other than the main components contained in the ceramic raw material include SiO2, SrCO3, Al ₂ O ₃ , MgCO ₃ and cordierite.

When the silicon carbide is used as the main component of the ceramic raw material, the silicon carbide is sintered by firing. When the metallic silicon and the silicon carbide particles are used as the main components of the ceramic raw material, the silicon carbide particles are bonded to each other as an aggregate with the metallic silicon as a binder by firing.

When the silicon carbide particles (the silicon carbide powder) and the metal silicon particles (the metal silicon powder) are used as the ceramic raw materials, the mass of the metal silicon particles based on the total mass of the silicon carbide particles and the metal silicon particles is preferably 10 to 40 mass%. The silicon carbide particles preferably have an average particle size of 10 to 50 µm, and more preferably 15 to 35 µm. The metallic silicon particles preferably have an average particle size of 0.1 to 20 µm, and more preferably from 1 to 10 µm. The average particle size of each of the silicon carbide particles and the metal silicon particles is a value measured by a laser diffraction method.

The examples of the organic binder include methyl cellulose, glycerin and hydroxypropylmethyl cellulose. As the organic binder, one type of organic binder can be used, or plural types of organic binder can be used. An amount of the added organic binder is preferably 5 to 10 parts by mass when the total mass of the ceramic raw materials 100 Mass fractions is.

As the surfactant, ethylene glycol, dextrin and the like can be used. As the surfactant, one type of surfactant can be used, or plural types of surfactants can be used. An amount of the surfactant mixed is preferably 0.1 to 2.0 parts by mass when the total mass of the raw materials is ceramic 100 Mass fractions is.

The sintering aid that can be used includes SiO ₂ , SrCO ₃ , Al ₂ O ₃ , MgCO ₃ , cordierite and the like. As the sintering aid, one type of sintering aid can be used, or plural types of sintering aid can be used. The amount of the admixed sintering aid is preferably 0.1 to 3 parts by mass, if the total mass of the ceramic raw materials 100 Mass fractions is.

The pore former is not particularly limited as long as it forms pores after firing. The examples include graphite, starch, foamed resins, water-absorbent resins and silica gel. As the pore builder, one type of pore builder can be used, or plural types of pore builders can be used. The amount of the added pore former is preferably 0.5 to 10 parts by mass, if the total mass of the ceramic starting materials 100 Mass fractions is.

An amount of the added water is preferably 20 to 60 parts by mass when the total mass of the raw materials of ceramics 100 Mass fractions is.

When the molding raw material is extruded, the molding raw material is first kneaded to form a green compact. The green compact is then extruded to obtain a honeycomb molded product. The honeycomb molding has a porous partition 15th on that the cells 14th defined, each from the fluid inflow end face 13a to the fluid outflow face 13b extend, and is in the middle with the second flow path 16 Mistake. The partition 15th of the honeycomb molding is a non-dried and non-fired partition 15th .

(Manufacturing step of a dried honeycomb body)

In the step of a dried honeycomb body, the resulting honeycomb molding is first dried to produce a dried honeycomb body. The drying conditions are not particularly limited, and known conditions can be used. It is Z. B. preferred to dry the honeycomb molding for 0.5 to 5 hours at a temperature of 80 to 120 ° C.

(Manufacturing step of a honeycomb body with unfired electrodes)

In the manufacturing step of a honeycomb body with unfired electrodes, an electrode molding paste containing the ceramic raw material and water is first applied to the side surface of the dried honeycomb body. The electrode molding slurry is then dried to form unfired electrodes and produce a honeycomb body with unfired electrodes.

For the honeycomb body with unfired electrodes, the dried honeycomb body is preferably provided with wide rectangular unfired electrodes, each of which is in a band shape in the extension direction of the cells 14th extend and also spread in a circumferential direction. The circumferential direction refers to a direction along the side surface of the dried honeycomb body in cross section orthogonal to the direction of extension of the cells 14th .

The electrode formation slurry used in the manufacturing step of the honeycomb body with unfired electrodes contains a ceramic raw material and water. The electrode formation slurry may contain a surfactant, a pore former, water, and the like.

It is preferable to use, as the ceramic raw material, the ceramic raw material used in manufacturing the honeycomb molding. If z. For example, if the main components of the ceramic raw material used in manufacturing the honeycomb molding are silicon carbide particles and metallic silicon, the silicon carbide particles and metallic silicon can also be used as the ceramic raw materials of the electrode formation slurry.

A method of applying the electrode formation slurry to the side surface of the honeycomb dried body is not particularly limited. The electrode formation slurry can e.g. B. can be applied using a brush or using a printing technique.

The electrode formation slurry preferably has a viscosity of 500 Pa · s or less, and more preferably 10 to 200 Pa · s at 20 ° C. The viscosity of the electrode formation slurry of 500 Pa · s or less can result in easy application of the electrode formation slurry to the side surface of the dried honeycomb body.

After applying the electrode formation slurry to the dried honeycomb body, the electrode formation slurry may be dried to obtain unfired electrodes (the honeycomb body with unfired electrodes). The drying temperature ranges preferably from 80 to 120 ° C. The drying time ranges preferably from 0.1 to 5 hours.

(Manufacturing step of honeycomb structure)

In the manufacturing step of a honeycomb structure, the honeycomb body with the unfired electrodes is fired to form the honeycomb structure 1 to manufacture.

The firing conditions can be appropriately determined according to the types of the ceramic raw material used in the production of the honeycomb molding and the ceramic raw material used in the electrode formation slurry.

Furthermore, calcination is preferably carried out after drying the honeycomb molding with the unfired electrodes and before firing in order to remove the binder and the like. The calcination is preferably carried out in an air atmosphere at a temperature of 400 to 500 ° C. for 0.5 to 20 hours.

When the urea hydrolysis catalyst 40 on the honeycomb structure 1 is worn, the honeycomb structure 1 z. B. be immersed in a container in which a slurry of the urea hydrolysis catalyst 40 is stored. By adjusting a viscosity of the slurry of the urea hydrolysis catalyst 40, a particle size of the contained urea hydrolysis catalyst 40 and the like, both the catalyst can be applied not only to the surfaces of the partition wall 15th , but also in the pores of the partition 15th are carried as well as adjusting an amount of the catalyst to be carried. Furthermore, the amount of the catalyst to be carried can also be adjusted by sucking in the slurry several times.

(2-2) Manufacture of the reducing agent injection device 100

The reductant injector 100 can be made by the honeycomb structure 1 in the outer cylinder 2 the honeycomb structure is used 1 over the insulation holding section 23 in the outer cylinder 2 is attached and the urea spray device 3 at one end (inlet-side end portion) of the outer cylinder 2 and then each of the connectors 18th of the outer cylinder 2 with each of the electrode terminal protruding portions 17th attached to the pair of electrode sections 12th are arranged over the electrical wiring 19th is connected.

Next, a method of using the reducing agent injection device will be discussed 100 of the present embodiment will be described in detail.

(3) Method of using the reducing agent injection device 100

The reductant injector 100 according to the present embodiment, the urea aqueous solution used as a raw material sprays from the urea sprayer 3 depending on the temperatures of the exhaust gas in the first flow path (the cells 14th ) or the second flow path 16 . When the temperature of the exhaust gas is lower, the urea aqueous solution selectively enters the first flow path (the cells 14th ) sprayed to the urea in the aqueous urea solution in the first flow path (the cells 14th ) to decompose to produce ammonia (reducing agent), the ammonia from the injection port 21 is injected to the outside. The flow through the honeycomb structure section becomes more specific 11 directed to increase the temperature (heating), the aqueous urea solution of the urea spray device 3 and the aqueous urea solution is fed from the urea spray device 3 in the first flow path (the cells 14th ) of the honeycomb structure section 11 sprayed. In this case, the flow of the urea aqueous solution can be prevented by the introduction of the carrier gas from the carrier gas introduction port 22nd to the fluid inlet face 13a of the honeycomb structure section 11 be conveyed in order to prevent the aqueous urea solution from entering the first flow path (the cells 14th ) of the honeycomb structure section 11 falters. The aqueous urea solution produced by the urea spray device 3 is sprayed occurs from the fluid inflow end face 13a according to the flow of the carrier gas in the first flow path (the cells 14th ) of the honeycomb structure section 11 a. the Urea in the aqueous urea solution that enters the first flow path (the cells 14th ) is fed in, is determined by the temperature of the heated honeycomb structure section 11 decomposed to produce the ammonia. On the other hand, when the temperature of the exhaust gas is higher, the urea aqueous solution becomes selectively in the second flow path 16 sprayed so that the aqueous urea solution from the injection port 21 is injected directly to the outside. In this case, by introducing the carrier gas from the carrier gas introduction port 22nd to the side of the fluid inflow end face 13a of the honeycomb structure section 11 the flow of the aqueous urea solution can be promoted in order to prevent the aqueous urea solution in the second flow path 16 of the honeycomb structure section 11 falters.

Here, the temperature of the exhaust gas is related to a required amount of the reducing agent. That is, when the temperature of the exhaust gas is higher, the required amount of the reducing agent is higher, while when the temperature of the exhaust gas is lower, the required amount of the reducing agent is lower. Therefore z. B. when the temperature of the exhaust gas is 200 ° C or higher, the urea aqueous solution from the urea spray device 3 in the second flow path 16 sprayed and injected outside as it is, while when the temperature of the exhaust gas is lower than 200 ° C, the urea aqueous solution from the urea spray device 3 in the first flow path (the cells 14th ) can be sprayed, whereby the generated ammonia can be sprayed to the outside.

The amount of the urea aqueous solution supplied is not particularly limited, and may preferably be an amount such that an equivalent ratio of ammonia to the amount of nitrogen oxides (NOx) contained in exhaust gas ranges from 1.0 to 2.0. If the equivalence ratio is less than 1.0, the amount of nitrogen oxides emitted without purification may increase. However, if the SCR catalytic converter is provided with a NOx storage function, there may be a period during which the equivalence ratio is less than 1.0. If the equivalence ratio is larger than 2.0, there is a risk that the exhaust gas is likely to be discharged with the ammonia mixed in the exhaust gas.

The urea aqueous solution is preferably an aqueous solution containing from 10 to 40 mass% of urea, although it is not particularly limited thereto. If the urea content is less than 10 mass%, it is necessary to spray a large amount of the urea aqueous solution in order to reduce NOx, with the amount of electric power required for conducting the current around the honeycomb structure portion 11 to warm up, can increase. If the urea content is larger than 40 mass%, there is a concern that the urea solidifies in cold areas. Preferred examples of the aqueous urea solution contain AdBlue (an aqueous solution containing 32.5 mass% of urea; a registered trademark of the German Association of the Automotive Industry (VDA)), which is widely used on the market.

The heating temperature of the honeycomb structure portion 11 is preferably 160 ° C or higher, and more preferably from 160 to 600 ° C, and even more preferably from 250 to 400 ° C. The heating temperature of 160 ° C or higher can cause the urea to decompose easily and efficiently. The heating temperature of 600 ° C or lower can allow the ammonia to be burned out and prevent the ammonia from being fed into the exhaust pipe. Further, it is preferable that the heating temperature of the honeycomb structure portion 11 360 ° C or higher because sulfur compounds such. B. ammonium hydrogen sulfate and ammonium sulfate, which are on the reductant injector 100 precipitated can be removed.

The maximum stress applied to the honeycomb structure section 11 is preferably from 12 to 200 V, and more preferably from 12 to 100 V, and even more preferably from 12 to 48 V. The maximum voltage of 12 V or greater can enable the temperature of the honeycomb structure portion 11 is simply increased. The maximum voltage of 200 V or less can prevent an apparatus for increasing the voltage from becoming expensive.

<Embodiment 2>

3 Fig. 13 is a schematic cross-sectional view showing a reducing agent injection device according to Embodiment 2 of the present invention (a schematic cross-sectional view parallel to an extending direction of cells of a honeycomb structure portion). Furthermore is 4th one along the line BB 'in 3 considered a schematic cross-sectional view (a schematic cross-sectional view perpendicular to the extending direction of the cells of the honeycomb structure portion) and FIG 5 one along the line CC 'in 3 considered schematic cross-sectional view (a schematic cross-sectional view parallel to the extension direction of the cells of the honeycomb structure portion).

As in the 3 until 5 shown is in a reductant injector 200 according to the present embodiment, the honeycomb structure 1 with the rectangular columnar honeycomb structure portion 11 in the outer cylinder 2 housed, being in the outer cylinder 2 the second flow path (an area of space 16 ) on one of the honeycomb structure 1 adjacent position is provided. Further is the reducing agent injection device 200 with a control valve 31 than the spray direction switch between the honeycomb structure 1 and the urea spray device 3 intended. The other configurations are the same as those of the reducing agent injection device 100 of Embodiment 1. Therefore, the descriptions of the other configurations will be omitted and only the differences will be described in detail.

In the reducing agent injector 200 according to the present embodiment are the first flow path through which the fluid in the cells 14th of the honeycomb structure section 11 can flow, and the second flow path, which is arranged adjacent to the first flow path and through which the fluid can flow, within the outer cylinder 2 intended. Because the second flow path 16 is configured so that the fluid passes through a different section than the cells 14th of the honeycomb structure section 11 can flow, the fluid flows either through the first flow path (the cells 14th ) or the second flow path 16 .

The control valve used as the spray direction switch 31 is not particularly limited as long as it can change the spray direction of the urea aqueous solution. 5 shows a state in which the control valve 31 the spray direction of the aqueous urea solution to the second flow path 16 controls. Because the control valve 31 the flow of the urea aqueous solution to the side of the first flow path (the cells 14th ) blocked, the aqueous urea solution can enter the second flow path 16 stream. On the other hand, if the flow of the urea aqueous solution to the second flow path side 16 through the control valve 31 is blocked, the aqueous urea solution can enter the first flow path (the cells 14th ) stream.

According to the reducing agent injection device 200 According to the present embodiment having the above structure, the urea aqueous solution can be supplied from the urea spray device 3 depending on the temperatures of the exhaust gas in the first flow path (the cells 14th ) or the second flow path 16 can be sprayed, so that the same effects as those of the reducing agent injection device 100 according to embodiment 1 can be obtained.

<Embodiment 3>

the 6th and 7th 13 are schematic cross-sectional views showing exhaust gas processing devices according to Embodiment 3 of the present invention.

As in the 6th and 7th shown includes each of the exhaust gas processing devices 300 and 400 according to the present embodiment: an exhaust pipe 41 through which the exhaust gas flows; the reductant injector 100 that is configured, the ammonia or the aqueous urea solution into the exhaust pipe 41 inject; and an SCR catalyst 42 on the exhaust pipe 41 is located on a downstream side of a position where the ammonia or the urea aqueous solution is injected.

The exhaust pipe 41 is a pipe through which an exhaust gas (exhaust gas containing NOx) discharged from various engines and the like is passed and in which the exhaust gas and ammonia are mixed. The size of the exhaust pipe 41 is not particularly limited and may depend on exhaust systems such. B. the engines on which the exhaust gas processing devices 300 and 400 according to the present embodiment are appropriately determined. The exhaust pipe 41 has a non-limiting length in the gas flow direction, but preferably has a length at which a distance between the reducing agent injector 100 and the SCR catalytic converter 42 can be set to a suitable distance.

A material of the exhaust pipe 41 is not particularly limited, but a material difficult to be corroded by the exhaust gas is preferred. Examples of the material of the exhaust pipe 41 contain stainless steel and the like.

In the reducing agent injector 100 is the injection port 21 on the exhaust pipe 41 attached that the ammonia or the aqueous urea solution in the exhaust pipe 41 injects. Specifically, the reducing agent injection device sprays 100 the aqueous urea solution into the exhaust pipe 41 when the temperature of the exhaust gas is 200 ° CC or higher while keeping the ammonia in the exhaust pipe 41 sprays when the temperature of the exhaust gas is less than 200 ° C, causing the ammonia or the aqueous urea solution in the exhaust pipe 41 is mixed into the exhaust gas. In addition, the in the exhaust pipe 41 sprayed aqueous urea solution is decomposed into ammonia by the heat of the exhaust gas.

As in 6th shown may be a reductant injector 100 on the exhaust pipe 41 to be appropriate. As in 7th is shown, two reductant injectors may also be on the exhaust line 41 to be appropriate. In this case, the reducing agent injection device on the downstream side may be the reducing agent injection device 100 or a conventional reductant injector 500 (e.g. the urea spray device 3 ), which the reducing agent (urea water) sprays without heating. In a preferred embodiment, the reducing spray device on the downstream side is the conventional reducing agent injecting device 500 that sprays the reducing agent (urea water) without heating. This is because when the amount of NOx in the exhaust gas is less (when the temperature of the exhaust gas is lower), most of the NOx passes through the reductant injector 100 and the SCR catalytic converter 42 on the upstream side is purified, while when the amount of NOx in the exhaust gas is higher (when the temperature of the exhaust gas is higher), that by the conventional reducing agent injection device 500 sprayed urea water is decomposed into ammonia by the temperature of the exhaust gas. Further, although not shown, three or more reducing agent injectors may be used as required 100 on the exhaust pipe 41 to be appropriate.

When the exhaust gas than that in the reducing agent injector 100 to be introduced carrier gas is used, as in the 6th and 7th shown is the exhaust pipe 41 upstream of the reductant injector 100 branched, with a branched flow path 43 with a carrier gas inlet opening 22nd connected is. On the other hand, when a carrier gas other than the exhaust gas (e.g. an inlet gas) is used, the carrier gas introduction port is 22nd connected to a carrier gas supply source via a connecting pipe or the like.

The SCR catalytic converter 42 in the form of a catalytic converter body (the honeycomb structure on which the SCR catalytic converter 42 is worn) is on the exhaust pipe 41 arranged downstream of the position at which the ammonia or the aqueous urea solution is injected. Therefore, as in 6th shown is the SCR catalytic converter 42 on the exhaust pipe 41 located on the downstream side of the position where the reducing agent injection device 100 attached when a reductant injector 100 on the exhaust pipe 41 is appropriate. If there are two reducing agent injectors on the exhaust pipe 41 are attached, the SCR catalytic converters 24 are on the exhaust pipe 41 located on the downstream side of the positions where the reducing agent injection device 100 or the conventional reducing agent injection device 500 are appropriate, as in 7th is shown.

The examples of the SCR catalytic converter 42 contain vanadium-based catalysts and zeolite-based catalysts.

If the SCR catalytic converter 42 is used as a catalyst body supported on the honeycomb structure, it is preferable that the catalyst body is contained in a container and the container on the exhaust pipe 41 is attached on the downstream side.

The honeycomb structure that makes up the SCR catalytic converter 42 is not particularly limited, and honeycomb structures known in the art can be used.

It is preferred that it be on the upstream side of the exhaust pipe 41 a filter is arranged to collect suspended matter in the exhaust gas. The examples of the filters for trapping particulate matter include e.g. B. a ceramic DPF (diesel particulate filter) 44 which has a honeycomb shape. It is also preferred that an oxidation catalyst 45 for removing hydrocarbons and carbon monoxide in the exhaust gas on the upstream side of the exhaust pipe 41 is arranged. The oxidation catalyst 45 is preferably in a state in which it is supported on a honeycomb structure made of ceramic (oxidation catalyst). The preferred examples of the oxidation catalyst 45 that can be used contain precious metals such as B. platinum (Pt), palladium (Pd) and rhodium (Rh).

When a reductant injector 100 on the exhaust pipe 41 attached are the DPF 44 and the oxidation catalyst 45 on the exhaust pipe 41 located on the upstream side of the position where the ammonia or urea aqueous solution passes through the reducing agent injection device 100 injected as in 6th is shown. Furthermore, if there are two reductant injectors 100 on the exhaust pipe 41 are attached to the DPF 44 and the oxidation catalyst 45 on the exhaust pipe 44 on the upstream side of the position where the ammonia or urea aqueous solution by the conventional reducing agent injection device 500 is injected, and on the downstream side of the SCR catalyst 42 on the downstream side of the position where the reducing agent injector 100 attached, arranged as in 7th is shown.

It is preferred to be on the downstream side of the SCR catalyst 42 to arrange an ammonia removing catalyst (oxidation catalyst) for removing the ammonia. Such an arrangement can prevent ammonia from being discharged to the outside when Excess ammonia, which has not been used to remove NOx in the exhaust gas, flows to the downstream side. The preferred examples of the oxidation catalyst, the one on the downstream side of the SCR catalyst 42 is arranged, contain precious metals, such as. B. platinum (Pt), palladium (Pd) and rhodium (Rh).

In the above description is the use of the reducing agent injection device 100 Embodiment 1 has been described. However, the reducing agent injection device can 200 of the embodiment can be used.

<Embodiment 4>

In a method for processing an exhaust gas according to Embodiment 4 of the present invention, when the temperature of the exhaust gas is 200 ° C or higher, the urea aqueous solution from the reducing agent injection device is released 100 , 200 Embodiment 1 or 2 is injected into the exhaust gas, wherein the exhaust gas mixed with the urea aqueous solution is reduced with the SCR catalyst, while when the temperature of the exhaust gas is lower than 200 ° C, the generated ammonia from the reducing agent injection device 100 , 200 Embodiment 1 or 2 is injected into the exhaust gas, the exhaust gas mixed with the ammonia being reduced with the SCR catalyst. The method of processing the exhaust gas can be performed using the exhaust gas processing device 300 , 400 according to the embodiment 3 simply run.

When the temperature of the exhaust gas is higher (when the temperature of the exhaust gas is 200 ° C. or higher), the reducing agent injection device sprays 100 , 200 selectively the urea aqueous solution, decomposing the urea aqueous solution by the heat of the exhaust gas to generate ammonia, thereby releasing the NOx through the SCR catalyst 42 can be cleaned. Therefore, when the temperature of the exhaust gas is higher, it is not necessary to pass through the reducing agent injection device 100 , 200 to increase the amount of ammonia generated, so that the power consumption can be reduced and the generation of urea scale can also be suppressed. On the other hand, when the temperature of the exhaust gas is lower (when the temperature of the exhaust gas is lower than 200 ° C), the ammonia can be selectively sprayed around the NOx through the SCR catalyst 42 to clean.

Because the carrier gas together with the aqueous urea solution produced by the urea spray device 3 is sprayed, can be supplied, the flow of the gas in the first flow path (the cells 14th ) or in the second flow path 16 of the honeycomb structure section 11 be promoted. As a result, it is possible to prevent urea from remaining in the first flow path or in the second flow path, so that the generation limit of urea scale can be increased. Further, when the temperature of the exhaust gas is lower than 200 ° C., the ammonia decomposed by the heating can be discharged outside with the carrier gas, so that the reactivity can be improved.

When the ammonia from the reductant injector 100 , 200 is sprayed (when the temperature of the exhaust gas is lower than 200 ° C), a temperature and a flow rate of the carrier gas and one of the honeycomb structure become 1 supplied power is preferably set so that a temperature of the fluid inflow end face 13a of the honeycomb structure portion 11,150 ° C or higher, and preferably 250 ° C or higher. To carry out such temperature control, e.g. B. the temperature of the carrier gas is preferably 100 ° C or higher and the flow rate is preferably 10 l / min or greater. The honeycomb structure 1 input power ranges preferably from 150 to 500 W.

An amount of the ammonia or aqueous urea solution released from the reductant injector 100 , 200 is injected is preferably such that the equivalent ratio of ammonia to the amount of nitrogen oxide contained in the exhaust gas ranges from 1.0 to 2.0. If the equivalence ratio is less than 1.0, the amount of nitrogen oxides emitted without purification may increase. If the equivalence ratio is larger than 2.0, there is a risk that the exhaust gas is likely to be discharged with the ammonia mixed in the exhaust gas.

It is preferable that the sprayed amount of the urea aqueous solution and the temperature (power supply) of the honeycomb structure portion 11 are controlled by an electronic control unit. Furthermore, the temperature can be determined from a resistance value of the honeycomb structure section 11 can be calculated, the temperature of the honeycomb structure portion 11 can be controlled so that the calculated temperature is a target temperature.

Industrial applicability

The reducing agent injection device, the exhaust gas processing device, and the method for processing the exhaust gas according to the present invention can be suitably used to purify the NOx in the exhaust gases emitted from various engines and the like.

List of reference symbols

1

Honeycomb structure

2

Outer cylinder

3

Urea spray device

11

Honeycomb structure section

12th

Electrode section

13a

Fluid inflow face

13b

Fluid discharge face

14th

cell

15th

partition wall

16

second flow path

17th

Electrode terminal protruding portion

18th

Interconnects

19th

electrical wiring

21

Injection port

22nd

Carrier gas inlet opening

23

Insulation holding section

31

Control valve

41

Exhaust pipe

42

SCR catalytic converter

43

branched flow path

44

DPF

45

Oxidation catalyst

100, 200

Reducing agent injection device

300, 400

Exhaust gas processing device

500

conventional reductant injector

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• JP 2007327377 A [0007]
• WO 2014/148506 [0007]
• JP 2017180298 A [0007]
• JP 2017180299 A [0007]

Claims (13)

A reductant injection device comprising: a honeycomb structure that includes: a columnar honeycomb structure portion having a partition wall defining a plurality of cells each extending from a fluid inflow end surface to a fluid outflow end surface; and at least one pair of electrode portions configured to heat the honeycomb structure portion by passing a current, the pair of electrode portions being arranged on a side surface of the honeycomb structure portion, the honeycomb structure configured to contain urea in an aqueous urea solution conducting the current can decompose heated honeycomb structure portion to produce ammonia; an outer cylinder having an inlet-side end portion and an outlet-side end portion, the inlet-side end portion including a carrier gas introduction port configured to introduce a carrier gas, the outlet-side end portion including an injection port configured to inject ammonia, the outer cylinder accommodating the honeycomb structure and a first flow path through which a fluid can flow through the plurality of cells and a second flow path through which the fluid can flow from the inlet-side end portion to the outlet-side end portion without passing through the plurality of cells are provided in the outer cylinder; a urea spray device configured to spray the urea aqueous solution into the first flow path or the second flow path on an inflow side of the fluid, the urea spray device being disposed at one end of the outer cylinder; and a spray direction switch configured to switch a spray direction of the urea aqueous solution into the first flow path or the second flow path depending on the temperatures of an exhaust gas. Reducing agent injection device according to Claim 1 wherein the urea in the urea aqueous solution sprayed into the first flow path is decomposed in the first flow path by the honeycomb structure portion heated by the flow of the flow to generate ammonia, and the ammonia is injected outside, and the in Aqueous urea solution sprayed the second flow path is injected directly to the outside. Reducing agent injection device according to Claim 1 or 2 wherein the second flow path is configured such that the fluid can flow through a different portion than the plurality of cells of the honeycomb structure portion. Reducing agent injection device according to one of the Claims 1 until 3 wherein the honeycomb structure portion is a hollow honeycomb structure portion configured so that the second flow path is located at a center in a cross section perpendicular to an extending direction of the cells. Reducing agent injection device according to one of the Claims 1 until 3 wherein the second flow path is provided at a position adjacent to the honeycomb structure. Reducing agent injection device according to one of the Claims 1 until 5 wherein the urea spray device includes a spray direction switch, and wherein the spray direction switch is a nozzle that can change a spray direction of the urea aqueous solution depending on the feed pressures of the urea aqueous solution. Reducing agent injection device according to one of the Claims 1 until 5 wherein the spray direction switch is provided between the honeycomb structure and the urea spray device, and the spray direction switch is a control valve that can change the spray direction of the urea aqueous solution. Reducing agent injection device according to one of the Claims 1 until 7th wherein the carrier gas is an exhaust gas. Reducing agent injection device according to one of the Claims 1 until 8th wherein the honeycomb structure portion has an electrical resistivity of 0.01 to 500 Ωcm. Reducing agent injection device according to one of the Claims 1 until 9 wherein the honeycomb structure portion contains a silicon-silicon carbide composite material or silicon carbide as a main component. Reducing agent injection device according to one of the Claims 1 until 10 wherein the honeycomb structure portion has an area per unit volume of 5 cm ² / cm ³ or more. An exhaust gas processing device comprising: an exhaust pipe through which an exhaust gas flows; the reducing agent injection device according to one of the Claims 1 until 11 configured to inject ammonia or an aqueous urea solution into the exhaust pipe; and an SCR catalyst attached to the exhaust cylinder on a downstream side of a Position is arranged at which ammonia or the aqueous urea solution is injected. A method of processing an exhaust gas, the method comprising: injecting an aqueous urea solution into the exhaust gas from the reductant injector according to any one of the Claims 1 until 11 and reducing the exhaust gas mixed with the urea aqueous solution by an SCR catalyst when a temperature of the exhaust gas is 200 ° C or higher; and injecting the generated ammonia into the exhaust gas by the reducing agent injection device and reducing the exhaust gas mixed with the ammonia by the SCR catalyst when a temperature of the exhaust gas is lower than 200 ° C.

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